U.S. patent number 10,128,115 [Application Number 12/713,356] was granted by the patent office on 2018-11-13 for method of forming ultra-shallow junctions in semiconductor devices.
This patent grant is currently assigned to TAIWAN SEMICONDUCTOR MANUFACTURING COMPANY, LTD.. The grantee listed for this patent is Chun-Feng Nieh, Chun Hsiung Tsai, Chii-Ming Wu, Mao-Rong Yeh. Invention is credited to Chun-Feng Nieh, Chun Hsiung Tsai, Chii-Ming Wu, Mao-Rong Yeh.
United States Patent |
10,128,115 |
Nieh , et al. |
November 13, 2018 |
Method of forming ultra-shallow junctions in semiconductor
devices
Abstract
A method of forming MOS transistor includes the steps of
performing a pocket implantation process on a substrate having a
gate stack, performing a co-implanted ion implantation process on
the substrate at a temperature less than room temperature,
performing a lightly doped source/drain implantation process on the
substrate, and forming source and drain regions in the substrate,
adjacent the gate stack.
Inventors: |
Nieh; Chun-Feng (Hsinchu,
TW), Yeh; Mao-Rong (Tao Yuan, TW), Tsai;
Chun Hsiung (Xinpu Township, TW), Wu; Chii-Ming
(Taipei, TW) |
Applicant: |
Name |
City |
State |
Country |
Type |
Nieh; Chun-Feng
Yeh; Mao-Rong
Tsai; Chun Hsiung
Wu; Chii-Ming |
Hsinchu
Tao Yuan
Xinpu Township
Taipei |
N/A
N/A
N/A
N/A |
TW
TW
TW
TW |
|
|
Assignee: |
TAIWAN SEMICONDUCTOR MANUFACTURING
COMPANY, LTD. (Hsinchu, TW)
|
Family
ID: |
44505511 |
Appl.
No.: |
12/713,356 |
Filed: |
February 26, 2010 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20110212592 A1 |
Sep 1, 2011 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L
21/26513 (20130101); H01L 21/823814 (20130101); H01L
21/26586 (20130101); H01L 29/6659 (20130101); H01L
21/26593 (20130101); H01L 21/26506 (20130101); H01L
29/1083 (20130101) |
Current International
Class: |
H01L
21/00 (20060101); H01L 29/66 (20060101); H01L
21/265 (20060101); H01L 21/8238 (20060101); H01L
29/10 (20060101) |
Field of
Search: |
;438/229,199 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Maldonado; Julio J
Assistant Examiner: Stevenson; Andre' C
Attorney, Agent or Firm: Hauptman Ham, LLP
Claims
What is claimed is:
1. A method, comprising: forming, by a pocket implantation process
on a substrate having a gate stack, a pocket implant region in the
substrate; forming a lightly-doped source/drain (LDD) region in the
pocket implant region by: performing a co-implanted ion
implantation process with a diffusion-reducing species at a
temperature less than room temperature and without performing a
pre-amorphisation implantation process, to form an amorphous
region, and performing a lightly doped source/drain implantation
process into the amorphous region; and performing a source/drain
implantation process into the amorphous region and the pocket
implant region following completion of the lightly doped
source/drain implantation process.
2. The method of claim 1, wherein no pre-amorphisation implantation
process is performed before or after the pocket implantation
process or the lightly doped source/drain implantation process.
3. The method of claim 1, wherein the pocket implantation process
is performed at a temperature not less than room temperature.
4. The method of claim 1, wherein the co-implanted ion implantation
process is performed at a temperature ranging between about
-100.degree. C. and about 0.degree. C.
5. The method of claim 1, wherein the lightly doped source/drain
implantation process is performed at a temperature not less than
room temperature.
6. The method of claim 1, wherein the diffusion-reducing species
comprises nitrogen, fluorine, carbon, or combinations thereof.
7. The method of claim 1, further comprising after completion of
the lightly doped source/drain implantation process, forming
spacers adjacent to the gate stack.
8. The method of claim 1, wherein the co-implanted ion implantation
process is performed by an ion implanter with a Cyro function.
9. A method of forming MOS transistors, the method comprising:
forming, by a pocket implantation process on a substrate having a
gate stack and free of a pre-amorphisation implant, a pocket
implantation region in the substrate; performing a co-implanted ion
implantation process with a diffusion-blocking dopant on the
substrate at a temperature less than about 0.degree. C. to form an
amorphous region within the pocket implantation region of the
substrate; performing a lightly doped source/drain implantation
process on the amorphous region; and performing a source/drain
implantation process following completion of the lightly doped
source/drain implantation process.
10. The method of claim 9, wherein no pre-amorphisation
implantation process is performed before or after the pocket
implantation process or the lightly doped source/drain implantation
process.
11. The method of claim 9, wherein the pocket implantation process
is performed at a temperature not less than room temperature.
12. The method of claim 9, wherein the co-implanted ion
implantation process is performed at a temperature not less than
about -100.degree. C.
13. The method of claim 9, wherein the lightly doped source/drain
implantation process is performed at a temperature not less than
room temperature.
14. The method of claim 9, wherein performing the co-implanted ion
implantation process includes implanting the substrate with implant
including nitrogen, fluorine, carbon, or combinations thereof.
15. The method of claim 9, further comprising, after completion of
the lightly doped source/drain implantation process, forming
spacers adjacent to the gate stack.
16. The method of claim 9, wherein the co-implanted ion
implantation process is performed by an ion implanter with a Cyro
function.
17. A method of forming MOS transistors comprising: performing a
pocket implantation process on a substrate having a gate stack
thereon at a temperature not less than about room temperature;
forming a lightly doped source/drain (LDD) region by: performing a
co-implanted ion implantation process with a diffusion-slowing
dopant to form amorphous regions in the substrate, wherein the
co-implanted ion implantation process is performed at a temperature
ranging between about -100.degree. C. and about 0.degree. C., and
performing a lightly doped source/drain implantation process on the
amorphous regions at a temperature not less than about room
temperature; and forming source and drain regions, following
completion of the lightly doped source/drain implantation process,
in the substrate, adjacent the gate stack, wherein a
pre-amorphisation implantation process is not performed before or
after the steps of pocket implantation or lightly doped
source/drain implantation; wherein performing the co-implanted ion
implantation process includes implanting the substrate with implant
including nitrogen, fluorine, carbon, or combinations thereof.
18. The method of claim 1, wherein the co-implanted ion
implantation process forms a trapping layer configured to prevent
interstitial back flow in the substrate.
19. The method of claim 1, wherein the lightly doped source/drain
implantation process is performed by an ion implant tilt process at
a tilt angle between about 0 degrees and 30 degrees.
20. The method of claim 1, wherein substantially equivalent implant
energies are used for the pocket implantation process and the
co-implanted ion implantation process.
Description
RELATED APPLICATIONS
The present disclosure is related to the following
commonly-assigned U.S. patent applications, the entire disclosures
of which are incorporated herein by reference: U.S. application
Ser. No. 12/616,406 or "METHOD FOR OBTAINING QUALITY ULTRA-SHALLOW
DOPED REGIONS AND DEVICE HAVING SAME" .
TECHNICAL FIELD
This invention is related generally to semiconductor devices, and
more particularly to the formation of Metal-Oxide Semiconductor
(MOS) devices with ultra-shallow junctions.
BACKGROUND
As the dimensions of transistors are scaled down, the reduction of
vertical junction depth and the suppression of dopant lateral
diffusion, in order to control short-channel effects, become
greater challenges. MOS devices have become so small that the
diffusion of impurities from lightly doped source/drain (LDD)
regions and source/drain regions will significantly affect the
characteristics of the MOS devices. Particularly, impurities from
LDD regions are readily diffused into the channel region, causing
short channel effects and leakage currents between the source and
drain regions.
Typically, when LDD regions are formed in a semiconductor substrate
by ion implantation, the junction depth is not just dependent on
the ion implant energy but can also depend on channeling and
phenomena such as transient enhanced diffusion (TED) when the
implanted ions migrate through the crystal lattice during
subsequent thermal processing. Current techniques for forming
ultra-shallow doped regions, such as p-type LDD (PLDD) regions in
PMOS devices and n-type LDD (NLDD) regions in NOMS devices, use
pre-amorphisation techniques to amorphise the semiconductor
substrate (i.e., turn a portion of the crystalline silicon
substrate into amorphous silicon) by, for example, ion implantation
using non-electrically active ions, such as silicon, germanium and
fluorine, in order to eliminate channeling. The pre-amorphization
implantation creates in the substrate an amorphous surface layer
adjacent to the underlying crystalline semiconductor material and
produces a large number of defects beyond the amorphous/crystalline
interface. These crystal defects are usually called End of Range
(EOR) defects. Defects of this kind are known to enhance diffusion
of previously implanted dopant ions during subsequent thermal
processes of annealing and activation of the semiconductor
device.
Methods for preventing the above-described EOR defects and
controlling the diffusion of implanted dopants are thus
explored.
BRIEF DESCRIPTION OF THE DRAWINGS
Aspects of the present disclosure are best understood from the
following detailed description when read with the accompanying
figures. It is emphasized that, in accordance with the standard
practice in the industry, various features are not drawn to scale.
In fact, the dimensions of the various features may be arbitrarily
increased or reduced for clarity of discussion.
FIG. 1 is a flow chart of a method of fabricating a semiconductor
device having ultra-shallow junctions according to various aspects
of the present disclosure; and
FIGS. 2A-2H are cross-sectional views of an embodiment of a
semiconductor device at various stages of fabrication according to
the method of FIG. 1.
DETAILED DESCRIPTION
In the creation of ultra-shallow junctions in Complementary
Metal-Oxide Semiconductor (CMOS) manufacturing, special attention
is not only given to forming the doped regions of source/drain
(S/D), but also focusing on the formation of lightly doped
source/drain (LDD) regions. To date, boron is the one candidate for
p-type dopant that has a high enough solid solubility to form the
doped regions with the required electrical conductivity. However
boron will diffuse rapidly in the silicon substrate during the high
temperature anneal ("activation") cycle that is required to process
the wafers. This anomalous boron diffusion, transient enhanced
diffusion (TED), limits the attainable parameters, in particular
the abruptness of the p-n junction, particularly that of the PLDD
regions. TED is believed to be mediated (detrimentally increased)
by defects created in the silicon during the implantation process,
as discussed above.
With reference to FIGS. 1 and 2A-2H, a method 100 and a
semiconductor device 200 are collectively described below. The
semiconductor device 200 illustrates an integrated circuit, or
portion thereof, that can comprise memory cells and/or logic
circuits. In some embodiments, the semiconductor device 200 can
include passive components such as resistors, capacitors,
inductors, and/or fuses; and active components, such as P-channel
field effect transistors (PFETs), N-channel field effect
transistors (NFETs), metal-oxide-semiconductor field effect
transistors (MOSFETs), complementary metal-oxide-semiconductor
transistors (CMOSs), high voltage transistors, and/or high
frequency transistors, other suitable components, and/or
combinations thereof. It is understood that additional steps can be
provided before, during, and/or after the method 100, and some of
the steps described below can be replaced or eliminated, for
additional embodiments of the method. It is further understood that
additional features can be added in the semiconductor device 200,
and some of the features described below can be replaced or
eliminated, for additional embodiments of the semiconductor device
200.
Referring to FIGS. 1 and 2A, the method 100 begins at block 102
wherein a substrate 202 is provided. In the present embodiment, the
substrate 202 is a semiconductor substrate comprising silicon. In
alternative embodiments, the substrate 202 comprises an elementary
semiconductor including silicon and/or germanium in crystal; a
compound semiconductor including silicon carbide, gallium arsenic,
gallium phosphide, indium phosphide, indium arsenide, and/or indium
antimonide; an alloy semiconductor including SiGe, GaAsP, AlInAs,
AlGaAs, GaInAs, GaInP, and/or GaInAsP; or combinations thereof. In
some embodiments, the alloy semiconductor substrate may have a
gradient SiGe feature in which the Si and Ge composition change
from one ratio at one location to another ratio at another location
of the gradient SiGe feature. The alloy SiGe may be formed over a
silicon substrate. The SiGe substrate may be strained. Furthermore,
in at least one embodiment, the semiconductor substrate may be a
semiconductor on insulator (SOI). In some examples, the
semiconductor substrate may include a doped epi layer. In other
examples, the silicon substrate may include a multilayer compound
semiconductor structure.
An exemplary isolation region 204 is formed in the substrate 202 to
isolate various regions of the substrate 202, and, in the present
embodiment for example, to isolate a PMOS device 240A and a NMOS
device 240B. The isolation region 204 utilizes isolation
technology, such as local oxidation of silicon (LOCOS) or shallow
trench isolation (STI), to define and electrically isolate the
various regions. In the present embodiment, the isolation region
204 includes a STI. In some embodiments, the isolation region 204
comprises silicon oxide, silicon nitride, silicon oxynitride, other
suitable materials, or combinations thereof. The isolation region
204 is formed by any suitable process. As one example, the
formation of an STI includes a photolithography process, etching a
trench in the substrate (for example, by using a dry etching and/or
wet etching), and filling the trench (for example, by using a
chemical vapor deposition process) with one or more dielectric
materials. In some examples, the filled trench may have a
multi-layer structure such as a thermal oxide liner layer filled
with silicon nitride or silicon oxide.
A material layer is formed over the substrate 202. The material
layer includes one or more material layers comprising any suitable
material and thickness. In some embodiments, the material layer can
include interfacial layers, capping layers, diffusion/barrier
layers, dielectric layers, high-k dielectric layers, conductive
layers, gate layers, liner layers, seed layers, adhesion layers,
other suitable layers, and/or combinations thereof. The material
layer is formed by any suitable process including chemical vapor
deposition (CVD), physical vapor deposition (PVD), atomic layer
deposition (ALD), high density plasma CVD (HDPCVD), metal organic
CVD (MOCVD), remote plasma CVD (RPCVD), plasma enhanced CVD
(PECVD), plating, other suitable methods, and/or combinations
thereof. In some embodiments, the semiconductor device 200 may
include one or more antireflective coating layers, such as a top
antireflective coating layer and/or a bottom antireflective coating
layer.
In one embodiment, the material layer includes a gate dielectric
layer and a gate electrode layer. The gate dielectric layer is
formed over the substrate 202 by any suitable process to any
suitable thickness. The gate dielectric layer, for example, is
silicon oxide, silicon oxynitride, silicon nitride, spin-on glass
(SOG), fluorinated silica glass (FSG), carbon doped silicon oxide,
Black Diamond.RTM. (Applied Materials of Santa Clara, Calif.),
Xerogel, Aerogel, amorphous fluorinated carbon, Parlyene, BCB
(bis-benzocyclobutenes), SiLK (Dow Chemical, Midland, Mich.),
polyimide, other suitable dielectric materials, or combinations
thereof. The gate dielectric layer may comprise a high-k dielectric
material, such as HfO.sub.2, HfSiO, HfSiON, HfTaO, HfTiO, HfZrO,
other suitable high-k dielectric materials, and/or combinations
thereof. The gate dielectric layer can further include an
interfacial layer, which comprises a grown silicon oxide layer
(e.g., thermal oxide or chemical oxide) or silicon oxynitride
(SiON).
The gate electrode layer is formed over the gate dielectric layer
by any suitable process to any suitable thickness. In the present
embodiment, the gate electrode layer is a polysilicon layer. The
polysilicon (or poly) layer is formed by CVD or other suitable
deposition process. For example, silane (SiH.sub.4) may be used as
a chemical gas in the CVD process to form the gate electrode
layer.
The gate electrode layer may include a thickness ranging from about
400 to about 800 angstrom (.ANG.). The gate electrode layer and the
gate dielectric layer are then patterned to form gate structures of
the PMOS 240A and the NMOS 240B. Each of the PMOS 240A and the NMOS
240B comprises the gate structure with a gate electrode 208
overlying a gate dielectric 206. In another embodiment, the gate
electrode 208 and/or the gate dielectric 206 may be sacrificial
layers and will be removed by a replacement step after the gate
patterning process.
Referring to FIGS. 1 and 2B, the method 100 continues with block
104 in which pocket/halo regions 210 are formed in the NMOS device
240B. The pocket/halo regions 210 are formed by an ion implantation
process 212 to introduce p-type dopants, such as boron, into the
substrate 202. In some embodiments, the ion implantation process
212 is preferably preformed by a tilt implant process at a tilt
angle ranging between about 0 degrees and about 60 degrees. In one
embodiment, the ion implantation process 212 is performed at an
energy ranging between about 10 KeV and about 100 KeV. In another
embodiment, the ion implantation process 212 is performed with a
dopant dosage ranging between about 1E13 atoms/cm.sup.2 and about
1E15 atoms/cm.sup.2. In yet another embodiment, the ion
implantation process 212 is performed at a temperature not less
than room temperature (room temperature being about 20.degree. C.
to 25.degree. C.). In some embodiments, the pocket/halo regions 210
may be partially under edges of the gate structure of NMOS device
240B because of the tilt implant process. As is known in the art,
more than one implantation may be conducted to form pocket/halo
regions 210 in desired regions. In at least one embodiment, p-type
pocket/halo regions 210 are preferably located around the side
borders and junction of the subsequently formed source/drain
regions (including LDD regions) to neutralize the diffusion of the
n-type impurities.
Referring to FIGS. 2C and 2D, a co-implanted ion implantation
process 214 and a lightly doped source/drain (LDD) implantation
process 218 are then provided to the NMOS 240B to form n-type
lightly doped source/drain (NLDD) regions 216 within the
pocket/halo regions 210. Referring to FIGS. 1 and 2C, the method
100 continues with block 106 in which the co-implanted ion
implantation process 214 is performed to introduce dopants, such as
nitrogen and/or fluorine, in the to-be-formed n-type lightly doped
source/drain (NLDD) regions 216. The co-implanted ion implantation
process 214 may result a trapping layer (not shown) in the
substrate 202 to prevent interstitial back flow in the NMOS device
240B.
In one embodiment, the co-implanted ion implantation 214 is
preferably preformed by an implant process at a tilt angle ranging
about 0 degrees and about 60 degrees. In another embodiment, the
ion implantation process is performed at energy ranging between
about 1 and about 20 KeV. In yet another embodiment, the ion
implantation process is performed with a dopant dosage ranging
between about 5E14 atoms/cm.sup.2 and about 2E15 atoms/cm.sup.2.
The co-implanted ion implantation process 214, for example, is
conducted at a low temperature such as at a temperature less than
room temperature in some embodiments, to form amorphous regions
(not shown) and co-implantation regions (not shown) within the
to-be-formed NLDD regions 216. In another embodiment, the
co-implanted ion implantation process 214 is performed at a
temperature ranging between about -100.degree. C. and about
0.degree. C. by adapting a Cyro (low temperature) function in the
ion implanter.
Low temperature co-implanted ion implantation process may form
amorphous regions, hence it is not necessary to apply a
pre-amorphization implantation process to the substrate. Therefore,
the process flow for device fabrication may be accordingly
simplified. In addition, the formation of a large number of defects
from the step of pre-amorphization implantation could be prevented
and the device performance could be enhanced.
Referring to FIGS. 1 and 2D, the method 100 continues with block
108 in which the lightly doped source/drain (LDD) implantation
process 218 is provided to the NMOS 240B to introduce n-type
dopants, such as phosphor or arsenic, to form the NLDD regions 216.
The LDD implantation process 218 is preferably preformed by an ion
implant process at a tilt angle ranging between about 0 degrees and
about 30 degrees. In one embodiment, the LDD implantation process
218 is performed at energy ranging between about 1 KeV and about 10
KeV. In another embodiment, the LDD implantation process 218 is
performed with a dopant dosage ranging between about 5E14
atoms/cm.sup.2 and about 2E15 atoms/cm.sup.2. In at least one
embodiment, the ion implantation process 218 is performed at a
temperature not less than room temperature.
Nitrogen and/or fluorine, introduced by the co-implanted ion
implantation 214, have the function of retarding the diffusion of
other dopants. Therefore, the diffusion of the dopants introduced
by the LDD implantation 218 is controlled when the MOS devices are
annealed, and thus the NLDD regions 216 have higher impurity
concentrations and more confined profiles for forming the
ultra-shallow junction.
Furthermore, it is understood that the PMOS device 240A may be
protected by a patterned photoresist or other suitable protection
pattern during the above-described implantation processes provided
to the NMOS device 240B.
FIGS. 2E-2G illustrate ion implantation processes to the PMOS
device 240A. Steps as explained in FIG. 1 apply to the formation of
the PMOS device 240A as well. Referring to FIG. 2E, pocket/halo
regions 222 are formed in the substrate 202 (Step 104). The
pocket/halo regions 222 are formed by an ion implantation process
220 to introduce n-type dopants, such as phosphor or arsenic, into
the substrate 202. The pocket/halo regions 222 are preferably
preformed by a tilt implant process at a tilt angle ranging about 0
degrees and about 60 degrees. In one embodiment, the ion
implantation process 220 is performed at energy ranging between
about 10 KeV and about 100 KeV. In another embodiment, the ion
implantation process 220 is performed with a dopant dosage ranging
between about 1E13 atoms/cm.sup.2 and about 1E15 atoms/cm.sup.2. In
yet another embodiment, the ion implantation process 220 is
performed at a temperature not less than room temperature. In some
embodiments, the pocket/halo regions 222 may be partially under
edges of the gate structure of PMOS device 240A because of the tilt
implant process. As is known in the art, more than one implantation
may be conducted to form pocket/halo regions 222 in desired
regions. In at least one embodiment, n-type pocket/halo regions 222
are preferably located around the side borders and junction of the
subsequently formed source/drain regions (including LDD regions) to
neutralize the diffusion of the p-type impurities.
Referring to FIGS. 2F and 2G, a co-implanted ion implantation
process 224 and a lightly doped source/drain (LDD) implantation
process 228 are provided to the PMOS 240A to form p-type lightly
doped source/drain (PLDD) regions 226 within the pocket/halo
regions 222. Referring to FIG. 2F, the co-implanted ion
implantation 224 process is performed to introduce dopants (Step
106), such as nitrogen and/or carbon, in the to-be-formed PLDD
regions 226. The co-implanted ion implantation process 224 may
result a trapping layer (not shown) in the substrate 202 to prevent
interstitial back flow in the PMOS device 240A.
In one embodiment, the co-implanted ion implantation process 224 is
preferably preformed by an ion implant process at a tilt angle
ranging about 0 degrees and about 60 degrees. In another
embodiment, the ion implantation process is performed at energy
ranging between about 1 KeV and about 20 KeV. In yet another
embodiment, the ion implantation process is performed with a dopant
dosage ranging between about 5E14 atoms/cm.sup.2 and about 2E15
atoms/cm.sup.2. In some embodiments, the co-implanted ion
implantation process 224 is preformed at a low temperature for
pre-amorphization and co-implantation formation. In some
embodiments, the term "low temperature" refers to a temperature
lower than room temperature, and preferably between about
-100.degree. C. and about 0.degree. C. The co-implanted ion
implantation process 224, for example, is conducted at a low
temperature to form amorphous regions (not shown) and
co-implantation regions (not shown) within the to-be-formed PLDD
regions 226. In one embodiment, the co-implanted ion implantation
process 224 is performed at a temperature less than room
temperature. In another embodiment, the co-implanted ion
implantation process 224 is performed at a temperature ranging
between about -100.degree. C. and about 0.degree. C. by adapting a
Cyro (low temperature) function in the ion implanter.
Low temperature co-implanted ion implantation process may form
amorphous regions, hence it is not necessary to apply a
pre-amorphization implantation process to the substrate. Therefore,
the process flow for device fabrication may be accordingly
simplified. In addition, the formation of a large number of defects
from the step of pre-amorphization implantation could be prevented
and the device performance could be enhanced.
Referring to FIG. 2G, a lightly doped source/drain (LDD)
implantation process 228 is performed to introduce p-type dopants,
such as boron, to form the PLDD regions 226. The LDD implantation
process 228 is preferably preformed by an ion implant process at a
tilt angle ranging between about 0 degrees and about 30 degrees. In
one embodiment, the LDD implantation process 228 is performed at
energy ranging between about 1 KeV and about 10 KeV. In another
embodiment, the LDD implantation process 228 is performed with a
dopant dosage ranging between about 5E14 atoms/cm.sup.2 and about
2E15 atoms/cm.sup.2. In at least one embodiment, the LDD
implantation process 228 is performed at a temperature not less
than room temperature.
Nitrogen, Fluorine and/or carbon, introduced by the co-implanted
ion implantation process 228, have the function of retarding the
diffusion of other dopants. Therefore, the diffusion of the dopants
introduced by the LDD implantation process 228 is controlled when
the MOS devices are annealed, and thus the PLDD regions 226 have
higher impurity concentrations and more confined profiles for
forming the ultra-shallow junction.
Furthermore, it is also understood that the NMOS device 240B may be
protected by a patterned photoresist or other suitable protection
pattern during the above-described implantation processes provided
to the PMOS device 240A.
In some embodiments, spaceres 230 are then formed as shown in FIG.
2H. Thereafter, source/drain (S/D) regions 234, 232 may be formed
in the substrate 202 by conventional implantation processes. One or
more thermal processes, such as rapid thermal anneal (RTA), may
also be provided on the substrate 202 to activate the dopants in
the S/D regions. The formation details are well known in the art,
thus are not repeated herein.
Subsequent processing in some embodiments may implement a gate
replacement process. For example, metal gates may replace the gate
electrode 208 (i.e., polysilicon gate layer) of the gate structures
of the PMOS/ NMOS devices 240A/240B. A first metal gate having a
first work function may be formed in the gate structure of the NMOS
devices 240B and a second gate structure having a second work
function may be formed in the gate structure of the PMOS devices
240A. The metal gates may comprise any suitable material including
aluminum, copper, tungsten, titanium, tantulum, tantalum aluminum,
tantalum aluminum nitride, titanium nitride, tantalum nitride,
nickel silicide, cobalt silicide, silver, TaC, TaSiN, TaCN, TiAl,
TiAlN, WN, metal alloys, other suitable materials, and/or
combinations thereof.
In some embodiments, the pre-amorphized implantations for reducing
the dopant channeling effect and enhancing dopant activation can be
omitted by adapting the low-temperature co-implanted ion
implantation. Hence, End of Range (EOR) defects caused by the
pre-amorphized implantations will not be introduced in the LDD
regions and ultra-shallow LDD regions with more precisely
controlled implanted dopant are achieved.
Although the invention has been described in terms of exemplary
embodiments, it is not limited thereto. Rather, the appended claims
should be construed broadly to include other variants and
embodiments of the invention that may be made by those skilled in
the art without departing from the scope and range of equivalents
of the invention.
* * * * *